Which should I get?

http://www.newegg.com/Product/Product.aspx?Item=N82E16822148371

Get this one. It's the same as the 500GB one you were looking at, but it's $25 less.

 

Yes.

Seriously, "better" or "best" depends on your requirements.

 

As far as cache goes, 8MB vs 16MB isn't a contest: they perform identically.

As far as RPM's go, the higher the RPM's, the faster the drive is. This is less pronounced on laptop drives because of the smaller platter area. I'd go with the 5400RPM part personally. It seems like size is really the most important factor, so you shouldn't worry about the nonexistent speed difference.

 

Get both

Go for the best of both worlds - size AND RPMs. I put this in my MBP and it has been sweet.

http://www.newegg.com/Product/Product.aspx?Item=N82E16822148374

 

...you may want to wait for the bugs to be worked out first...